A circle has a sector with area $\dfrac{4}{5}\pi$ and central angle $8^\circ$. What is the area of the circle? ${36\pi}$ $\color{#9D38BD}{8^\circ}$ ${\dfrac{4}{5}\pi}$
Answer: The ratio between the sector's central angle $\theta$ and $360^\circ$ is equal to the ratio between the sector's area, $A_s$ , and the whole circle's area, $A_c$ $\dfrac{\theta}{360^\circ} = \dfrac{A_s}{A_c}$ $\dfrac{8^\circ}{360^\circ} = \dfrac{4}{5}\pi \div A_c$ $\dfrac{1}{45} = \dfrac{4}{5}\pi \div A_c$ $A_c \times \dfrac{1}{45} = \dfrac{4}{5}\pi$ $A_c = \dfrac{4}{5}\pi \times 45$ $A_c = 36\pi$